Exemplary embodiments of the inventive concept relate to a high voltage generating circuit, and more particularly, to a high voltage generating circuit, an operating method thereof, and a nonvolatile memory device including the same.
Semiconductor memory devices are typically classified as volatile memory devices or nonvolatile memory devices. The volatile memory devices lose stored contents at power-off, while the nonvolatile memory devices retain stored contents even when power is removed or turned off. Nonvolatile memory devices may be formed of various types of memory cell transistors, and may be divided according to structures of the memory cell transistors. Examples of nonvolatile memory devices include flash memory, ferroelectric random access memory (FRAM), magnetic RAM (MRAM), a phase change RAM (PRAM), and the like.
Flash memory devices may be NOR type flash memory devices or NAND flash memory devices, according to the cell array structure. The structure of NOR flash memory devices is that each memory cell transistor is separately connected to a word line and a bit line. Accordingly, NOR flash memory devices generally have excellent random access time characteristics. The structure of NAND flash memory devices is that multiple memory cell transistors are connected in series, which may be referred to as a cell string structure. One cell string may necessitate one bit line contact. Accordingly, NAND flash memory devices generally have excellent integration characteristics.
A NOR flash memory device may store data in a channel hot electron manner, and erase data in a Fowler-Nordheim tunneling manner. A NAND flash memory device may store and erase data in the Fowler-Nordheim tunneling manner. Accordingly, the NOR and NAND flash memory devices may require higher voltage levels than a power supply voltage during erase, program and read operations. The high voltages are generated from charge pumps within the flash memory devices. Such charge pumps may constitute a high voltage generating circuit.